﻿using System.Net;
using System.Net.Sockets;

namespace Cleanuparr.Infrastructure.Extensions;

public static class IpAddressExtensions
{
    public static bool IsLocalAddress(this IPAddress ipAddress)
    {
        // Map back to IPv4 if mapped to IPv6, for example "::ffff:1.2.3.4" to "1.2.3.4".
        if (ipAddress.IsIPv4MappedToIPv6)
        {
            ipAddress = ipAddress.MapToIPv4();
        }

        // Checks loopback ranges for both IPv4 and IPv6.
        if (IPAddress.IsLoopback(ipAddress))
        {
            return true;
        }

        // IPv4
        if (ipAddress.AddressFamily == AddressFamily.InterNetwork)
        {
            return IsLocalIPv4(ipAddress.GetAddressBytes());
        }

        // IPv6
        if (ipAddress.AddressFamily == AddressFamily.InterNetworkV6)
        {
            return ipAddress.IsIPv6LinkLocal ||
                   ipAddress.IsIPv6UniqueLocal ||
                   ipAddress.IsIPv6SiteLocal;
        }

        return false;
    }

    private static bool IsLocalIPv4(byte[] ipv4Bytes)
    {
        // Link local (no IP assigned by DHCP): 169.254.0.0 to 169.254.255.255 (169.254.0.0/16)
        bool IsLinkLocal() => ipv4Bytes[0] == 169 && ipv4Bytes[1] == 254;

        // Class A private range: 10.0.0.0 – 10.255.255.255 (10.0.0.0/8)
        bool IsClassA() => ipv4Bytes[0] == 10;

        // Class B private range: 172.16.0.0 – 172.31.255.255 (172.16.0.0/12)
        bool IsClassB() => ipv4Bytes[0] == 172 && ipv4Bytes[1] >= 16 && ipv4Bytes[1] <= 31;

        // Class C private range: 192.168.0.0 – 192.168.255.255 (192.168.0.0/16)
        bool IsClassC() => ipv4Bytes[0] == 192 && ipv4Bytes[1] == 168;

        return IsLinkLocal() || IsClassA() || IsClassC() || IsClassB();
    }
}